P1302: SALVAGE ALLOGENEIC HEMATOPOIETIC STEM CELL TRANSPLANTATION IS ALSO THE CURATIVE AND SAFE TREATMENT FOR RELAPSED/REFRACTORY ACUTE MYELOID LEUKEMIA IN THE ERA OF TARGETED THERAPY
Journal: HemaSphere (2023)

Topic: 22. Stem cell transplantation - Clinical Background: In the age of targeted drugs and CART therapy, the treatment of relapsed/refractory acute myeloid leukemia (r/r AML) has been greatly improved, however, most of these patients still cannot get complete disease clearance and long-term leukemia-free survival (LFS). Therefore, salvage allogeneic hematopoietic stem cell transplantation (allo-HSCT) is also the only curative treatment currently for these patients. Aims: We evaluated the efficacy and safety of salvage allo-HSCT for r/r AML. Methods: Between January 2020 and December 2022, 36 patients with r/r AML who received salvage allo-HSCT in our hospital were included. The median age was 37.6(4-69) years old. The average proportion of leukemia cells before transplantation in 32 patients was 26.1%, and 4 patients was simple extramedullary relapse. 9 patients had received one previous transplant and 1 patient had received two transplants before included. 3 patients received transplantation from unrelated donor (URD), 3 patients from matched-sibling donor (MSD), and the rest 30 patients received haploidentical donor (HID). The conditioning regimens were BU/FLAG or BU/CLAG (busulfan (3.2mg/kg x 3)/ cytarabine (1g/m2 x 5)/fludarabine (30mg/m2 x 5) or cladribine (5mg/m2 x 5) in 26 patients in first transplantation, and TBI/FLAG or TBI/CLAG (total body irradiation ((fractionated, total 8 Gy))/cytarabine/fludarabine or cladribine in 10 patients in second/third transplantation. Cyclosporine, mycophenolate mofetil and short-term methotrexate were employed for graft-versus-host disease (GVHD) prophylaxis. After transplantation, we give demethylating drugs, molecular targeted drugs, immunomodulatory drugs and other means to reduce recurrence and maintain remission. Results: The median follow-up time was 8.6 (0-30) months. The time of leukocyte reconstitution ranged from +8d to +24d in 31 patients, unfortunately the rest 5 patients died of infection due to failed leukocyte reconstitution. 25 patients got complete remission (CR) after transplantation in which 21 achieved MRD negative complete remission (MRD-CR). But 11 patients who did not respond died of leukemia, infection, or bleeding. 14 patients had mild acute GVHD, 1 patient had severe acute GVHD and 4 patients developed chronic GVHD. Most of them were resolved with immune-suppressants. 11 patients had CMV reactivation and 1 patient had EBV reactivation. 9 patients had mild hemorrhagic cystitis. As of press time, 17 patients have died, of which 6 patients died of leukemia, 6 patients died of infection, 1 patient died of bleeding, and 4 patients lost contact. The non-relapse mortality (NRM) was 19.4% (7/36). The 2-year leukemia free survival (LFS) and overall survival (OS) were 48.6% and 56.4% respectively. For the 10 patients who had previous transplantation, their median age was 31.5 years (14-46),. 4 of them survived (5-14months) and 6 patients died early after transplantation within 3 months, including 1 death from leukemia, 2 failed hematopoietic reconstructions, 1 severe infection, 1 severe GVHD, and 1 gastrointestinal bleeding. Both 1-year leukemia free survival (LFS) and overall survival (OS) were 40%. Summary/Conclusion: Our results indicate that salvage allogeneic hematopoietic stem cell transplantation is still the most effective therapeutic method for r/r AML. The 2-year leukemia free survival (LFS) and overall survival (OS) can reach to 48.6% and 56.4%. The non-relapse mortality (19.4%) was low, even we included 10 patients received the second/third salvage transplantation. Furthermore, for all the patients who cannot get remission after relapse post allo-HSCT we changed donors in the second transplantation, and then the second transplant can make them get MRD negative remission again and long-termsurvive.Keywords: relapsed/refractory, Salvage therapy, Hematopoietic cell transplantation, Acute myeloid leukemia